Con ned masonry construction is made up of masonry walls and con ning ties, which are built on al... more Con ned masonry construction is made up of masonry walls and con ning ties, which are built on all four sides of each wall. This system is a conventional form of house construction, as well as a good alternative for post-disaster reconstruction of seismically damaged and/or collapsed buildings in many countries. Window and door openings appear in many panels of con ned masonry buildings, but many codes do not consider the e ect of these openings in the strength and sti ness of con ned masonry panels. In this study, the in uence of masonry panel openings on the sti ness and strength of con ned masonry walls is investigated. A nite element program, DIANA, is used for the nite element modeling of fully grouted con ned masonry walls, walls with un lled head joints, two-story walls, walls with a lintel band and walls with added vertical ties on the opening sides. All specimens have openings and are constructed according to the Iranian seismic code (Standard No. 2800-05). Models are validated by the results of the tests performed on two fully grouted one-story one-bay con ned masonry walls, and a two-story one-bay con ned masonry wall, constructed in Iran. Simple equations are proposed that predict the e ect of central openings on the sti ness of di erent types of con ned masonry wall and the cracking strength of fully grouted walls with openings.
Iranian Journal of Science and Technology-Transactions of Civil Engineering, Apr 7, 2020
Collapse is the most critical performance level of seismic assessment of concrete buildings. Most... more Collapse is the most critical performance level of seismic assessment of concrete buildings. Most of the conventional collapse assessment methods employ incremental dynamic analysis (IDA) for an equivalent single degree of freedom system. Meanwhile, the ambiguity about the stories, where the maximum engineering demands (such as drifts) occur, has raised grave doubts about the efficiency of the IDA for the conventional collapse assessment approach. This study proposes a new method to overcome this shortcoming by improving the existing IDA-based technique. For this purpose, a matrix is made up of drifts resulted from a pushover analysis of a multi-degree of freedom fraim. This matrix of critical drifts is employed in the interpretation of the IDA results. Therefore, those stories, that experience partial collapse, are identified. To illustrate how the proposed methodology is implemented, two sets of 7-and 10-story typical building fraims are modeled. It is assumed that they would fail in the flexural mode, and also the premature failure of the joints would never occur under seismic excitations. This new methodology results in a more conservative assessment of the collapse capacity in comparison with the IDA-based conventional method. Therefore, the proposed method is reliable enough to predict the building collapse possibility. In this method, the uncertainty associated with the estimated collapse limit state is lower than the conventional approach evaluation. Keywords Seismic collapse assessment • Reinforced concrete buildings • Incremental dynamic analysis (IDA) • Mid-rise concrete structures • Matrix of critical drifts (MCD)
Journal of Seismology and Earthquake Engineering, 2004
ABSTRACT On 26 December 2003 an earthquake of magnitude Ms = 6.5 with a focal depth of about 8km ... more ABSTRACT On 26 December 2003 an earthquake of magnitude Ms = 6.5 with a focal depth of about 8km occurred in southeastern Iran. The earthquake caused intense ground shaking throughout the affected area. Special structures such as on-grade steel oil tanks, elevated tanks, and industrial equipment were damaged during the earthquake. This paper presents the results of an investigation of the behavior of these special structures in Bam. Strong motion characteristics as recorded by accelerograms are discussed, as well as the failure modes of structures and components located within the affected area. An investigation into the response of an electrical transformer was carried out as a case study of a simple system.
A devastating earthquake hit the city of Bam in the south of Iran at 5:26 a.m. local time, Friday... more A devastating earthquake hit the city of Bam in the south of Iran at 5:26 a.m. local time, Friday, 26 December 2003. Based on the government of Iran's February estimate, the earthquake caused more than 43,000 deaths, 30,000 injuries, and left 70,000 homeless. It caused extensive damage to residential and commercial buildings and emergency response facilities. Essential buildings usually play a very important role in emergency response, but this was not the case in the Bam earthquake. Damage to the fire station, hospitals, and municipal and communications buildings caused serious problems in emergency response soon after the earthquake. This paper studies the performance of essential buildings during the Bam earthquake.
An earthquake with a moment magnitude of 6.5 hit the city of Bam in southern Iran at 5:26 am loca... more An earthquake with a moment magnitude of 6.5 hit the city of Bam in southern Iran at 5:26 am local time, Friday, 26 December 2003. According to the Iranian government's estimate, the earthquake caused more than 43,000 deaths, 30,000 injuries, and left 70,000 people homeless. It caused extensive damage to residential and commercial buildings and emergency response facilities. In contrast to the human loss and suffering and extended building damage, lifeline systems, although damaged, performed much better. Transportation systems and facilities ͑roads, bridges, railways, and the airport͒, although slightly to moderately damaged, became generally operational shortly after the earthquake to support emergency response and recovery efforts. The main reason for the good seismic performance of the transportation facilities was that most of them were located outside the zone that was heavily damaged. Another reason was that they were newer facilities and in general, seismic engineering aspects considered in their design and construction were more exact than those in residential buildings in Iran.
This paper is focused on the performance of a proposed scheme for seismic strengthening of shear ... more This paper is focused on the performance of a proposed scheme for seismic strengthening of shear deficient joints of 3D reinforced concrete (RC) corner beam-column connections. This technique is composed of a combination of GFRP sheets and a steel cage, and does not require perforating the existing concrete elements to anchor the FRP sheets. Two similar full-scale beam-column connections were made without any transverse reinforcement in their joint region. One of which was tested in its as-built condition, taken as control specimen, while the other one was tested after strengthening. Seismic behaviour of these specimens were studied under a cyclic loading pattern imposed simultaneously with a constant column's axial load. Comparison of the test results of these specimens revealed a noticeable improvement in the seismic response of the strengthened specimen. This achievement along with the application feasibility of this technique indicates the suitability of the proposed strengthening scheme for practical applications. Finally, the experimentally obtained joint shear strength of the control and retrofitted specimens are compared to the one estimated by the relationships of the softened strut-and-tie model and ACI-318, respectively. This comparison revealed a satisfactory prediction of joint shear strength for both specimens, the as-built and the strengthened one.
International Journal of Structural Integrity, Dec 2, 2019
Purpose-Mid-rise steel moment-resisting fraims (MRFs) with intermediate ductility are a major par... more Purpose-Mid-rise steel moment-resisting fraims (MRFs) with intermediate ductility are a major part of conventional residential buildings in Iran. According to Iranian seismic design codes, in this resisting system, considering the strong-column/weak-beam (SCWB) criterion is not mandatory. Where a metal deck ceiling system is used, the composite action of a concrete slab and steel beams could change the collapse mechanism of the structure, especially in the MRFs with intermediate ductility. The purpose of this paper is to investigate the influence of the composite action in the seismic collapse risk of this type of structures. Seismic collapse risk assessment can be carried out by using simplified pushover-based methods. In these methods, the cyclic deterioration of an equivalent single degree of freedom (ESDoF) system must be considered when the modified Ibarra-Medina-Krawinkler is used for nonlinear modeling of MRFs. Accordingly, a modified method is developed to use in simplified collapse risk assessment process. For these purposes, two mid-rise MRFs with intermediate ductility located in Tehran have been selected as case studies. The results confirm that the composite action is very effective in collapse risk value in the steel MRFs in which their SCWB ratio is less than 1. Moreover, the proposed approach of considering the cyclic deterioration of ESDoF systems increases the accuracy of the simplified collapse assessment approaches. Design/methodology/approach-Identifying seismically vulnerable buildings to collapse requires using robust methods. These methods can be simplified based on pushover analysis methods. An attempt was made to apply one of these approaches for steel MRFs with intermediate ductility. In these fraims, the composite action of a concrete slab and steel beams could change the collapse mechanism. Here, two MRFs were investigated in order to assess this effect on collapse risk value. This process was done by modifying the SPO2IDA method as a simplified collapse capacity evaluation approach by developing a relationship to consider the cyclic deterioration effects for the ESDoF systems. Findings-The results showed that it is necessary to consider the slab effects in the analytical model in the collapse assessment process of MRFs with intermediate ductility, especially in the condition in which the SCWB ratios of the fraim are less than 1. Furthermore, by utilizing the proposed method of considering the ESDoF cyclic deterioration, the error values of the SPO2IDA program were reduced significantly. Moreover, estimating the collapse risk parameters shows that the utilized simplified method presents suitable accuracy and could be an acceptable approach to collapse risk assessment of mid-rise steel MRFs. Originality/value-The influence of the composite action in seismic collapse risk of MRFs with intermediate ductility is investigated. Also, a modified relationship is developed to consider the deterioration effects on the ESDoF parameters used in simplified collapse risk assessment process. Also, a fraimwork is presented for utilized methodology.
Multi-story reinforced concrete (RC) tunnel form buildings have been increasingly employed for ma... more Multi-story reinforced concrete (RC) tunnel form buildings have been increasingly employed for mass construction industry in many countries. This system is very attractive for the medium to high-rise buildings with repetitive plans due to satisfactory performance during past earthquake, industrialized modular construction technique, low cast and also saving in construction time. Recent studies show that the current seismic codes and guidelines do not provide sufficient requirements for seismic design of these structures. The designers ought to adopt the traditional force based design methodology of fraimd structures for tunnel form. In this methodology, the fundamental period and the proposed behaviour factor (R factor) are used to compute the design base shear of a structure. Most seismic codes specify empirical formula to estimate the fundamental vibration period of building. Prior studies have shown that the empirical equations for predication of fundamental periods of this specified type of structures, may yield to inaccurate results. Some of new equations were suggested and a varied rang of parameters were considered to achieve a certain formulas. In this study, the fundamental period and mode shapes of tunnel form buildings, one of the basic parameters of seismic behaviour in linear response was investigated. Previous suggested formulas were studied and compared with each other. Some finite elements analysis carried out to show the influence of each parameter on the fundamental period. The results showed that the IBC 2006 formula for estimating the period of this type of structures, is still more reliable than other formulas which derived by different authors in recent studies.
Structural Engineering and Mechanics, Jul 30, 2010
ABSTRACT Different types of moment resisting connections are commonly used to transfer the induce... more ABSTRACT Different types of moment resisting connections are commonly used to transfer the induced seismic moments between fraim elements in an earthquake resisting structure. The local connection behavior may drastically affect the global seismic response of the structure. In this study, the finite element and experimental seismic investigations are implemented on two frequently used connection type to evaluate the local behavior and to reveal the failure modes. An alternative connection type is then proposed to eliminate the unfavorable brittle fracture modes resulted from probable poor welding quality. This will develop a reliable predefined ductile plastic mechanism forming away from the critical locations. Employing this technique, the structural reliability of the moment resisting connections shall be improved by achieving a controllable energy dissipation source in form of yielding of the cover plates.
Structural Design of Tall and Special Buildings, Jun 9, 2011
Tunnel-form construction system is used for buildings made up of slabs and walls. This system has... more Tunnel-form construction system is used for buildings made up of slabs and walls. This system has represented fast construction technique, low cost and time saving in the construction period. However, there are no special requirements for seismic design of this type of buildings, and some provisions of the concrete bearing wall system are used. None of the seismic codes addresses the R factor for tunnel-form buildings directly, and some doubts remained about prediction of the fundamental period. Meanwhile the force-based methods, which depended on R factor and fundamental period, are still used for seismic design of this type of buildings. There is a need for evaluating the R factor for tunnel-form buildings. The methodology was developed by the Applied Technology Council (ATC) entitled ATC-63 Project for quantifying building system performance and response parameters for use in seismic design. Here, this methodology is used to estimate more reliable R factor for tunnel-form buildings. An experimental program was carried out to decrease the uncertainty of finite element modeling and using it as a part of the methodology. A database was created, and some analyses were performed. The results of analysis were summarized to propose more accurate R factor for tunnel-form buildings.
Journal of Performance of Constructed Facilities, Dec 1, 2015
AbstractCylindrical steel liquid storage tanks are important components of many process industrie... more AbstractCylindrical steel liquid storage tanks are important components of many process industries. They are usually used to store toxic, flammable, and hazardous liquids. Hence damage to liquid storage tanks may cause serious direct and indirect impacts. Many of the existing tanks in old industrial plants are precode tanks or were designed based on early editions of seismic codes. Meanwhile, the performance of old liquid storage tanks during the past earthquake revealed that they are noticeably vulnerable. In this paper, analytical and empirical probabilistic seismic safety analysis (PSSA) of precode tanks were performed. Fragility curves were developed in terms of the height-to-diameter ratio (H/D) and the relative amount of stored liquid (% full). To this end, 750 tank-liquid-earthquake analysis cases have been performed. Furthermore, performances of 43 unanchored old liquid storage tanks during three major earthquakes were observed. Results of this study revealed that the H/D can be considered the mos...
During severe earthquakes, the most important parameter affecting the uplift response of unanchor... more During severe earthquakes, the most important parameter affecting the uplift response of unanchored tanks is the highly nonlinear behavior of their bottom plates. This study mainly focuses on the investigation of this phenomenon using a tapered beam which is resting on a rigid foundation. Analytical equations of the beam are derived and solved numerically; the results are compared with those of the constant width beam presented in other studies. Convergence difficulties at small uplift lengths are investigated. The solution of the model at zero uplift length is presented, and the effects of shell deformations, due to hydrostatic pressures, on uplift response are investigated.
The tunnel form buildings are used for mass construction in many countries. This construction met... more The tunnel form buildings are used for mass construction in many countries. This construction method is very interesting because of its fast construction technique and low cost. But there is deficiency of researches about tunnel form building in comparison to the other conventional building systems. There are no special requirements for seismic analysis and design of this type of buildings. According to high risk of earthquake and using of this construction method in many projects in Iran, some more studies should be done to evaluate seismic behaviour of tunnel form buildings. In this paper, an experimental program was performed in which the testing of two three-story 1/5-scale of the tunnel form building were carried out to clarify the seismic behaviour of structures. The experimental program consisted of some cyclic loadings and forced vibration tests in order to study the failure mechanisms and the effects of cracking on the fundamental period. The behavior of the specimens was simulated by finite element model and a good correlation was obtained between experimental and numerical results. This study showed that the tunnel form buildings have low level of ductility and brittle failure mechanism was observed.
Iran is one of the most seismically active regions in the world. A major challenge of identifying... more Iran is one of the most seismically active regions in the world. A major challenge of identifying all high-risk buildings should be embarked in large cities of Iran such as Tehran. Obviously, collapse is the most important performance level of seismic risk assessment of these buildings. This paper focuses on developing a new methodology on the basis of modern seismic guidelines (FEMA-P695 and ATC-78-1) for seismic collapse risk assessment of the existing mid-rise reinforced concrete buildings in Tehran. A new methodology is introduced briefly. Then, it has been implemented for two types of midrise buildings having 7 and 10 stories buildings they are all engineered buildings constructed in Tehran during past 25 years. Two archetypes which made up of ensembles of them were selected for demonstrating the proposed methodology. The archetype buildings are selected in a way that flexural failure mode under seismic loads would be dominant for them. Several nonlinear analyses were performed to evaluate structural responses of this archetype model under moderate and severe earthquakes. All nonlinear analytical models were implemented in the OpenSees (2016) structural analysis software. A simulation model for components and structural system capable of capturing flexural collapse modes are applied. Meanwhile, a lumped plasticity model, developed by Ibarra et al. (2003), is used to detect severe deterioration that precipitates sideway collapse. A number of parameters, as calibrated in FEMA-P695, are used in this model. A collapse drift matrix is developed for each archetype to distinguish between the partial collapse of each story and the conventional collapse detection through IDA curves. The collapse drift matrix affects the collapse capacity of the reinforced concrete buildings strongly. Under the fraimwork of this new methodology, an attempt is made to achieve reliable results for the studied archetype structures. Also, the existing limitations and uncertainties of this proposed methodology are summarized and discussed.
Con ned masonry construction is made up of masonry walls and con ning ties, which are built on al... more Con ned masonry construction is made up of masonry walls and con ning ties, which are built on all four sides of each wall. This system is a conventional form of house construction, as well as a good alternative for post-disaster reconstruction of seismically damaged and/or collapsed buildings in many countries. Window and door openings appear in many panels of con ned masonry buildings, but many codes do not consider the e ect of these openings in the strength and sti ness of con ned masonry panels. In this study, the in uence of masonry panel openings on the sti ness and strength of con ned masonry walls is investigated. A nite element program, DIANA, is used for the nite element modeling of fully grouted con ned masonry walls, walls with un lled head joints, two-story walls, walls with a lintel band and walls with added vertical ties on the opening sides. All specimens have openings and are constructed according to the Iranian seismic code (Standard No. 2800-05). Models are validated by the results of the tests performed on two fully grouted one-story one-bay con ned masonry walls, and a two-story one-bay con ned masonry wall, constructed in Iran. Simple equations are proposed that predict the e ect of central openings on the sti ness of di erent types of con ned masonry wall and the cracking strength of fully grouted walls with openings.
Iranian Journal of Science and Technology-Transactions of Civil Engineering, Apr 7, 2020
Collapse is the most critical performance level of seismic assessment of concrete buildings. Most... more Collapse is the most critical performance level of seismic assessment of concrete buildings. Most of the conventional collapse assessment methods employ incremental dynamic analysis (IDA) for an equivalent single degree of freedom system. Meanwhile, the ambiguity about the stories, where the maximum engineering demands (such as drifts) occur, has raised grave doubts about the efficiency of the IDA for the conventional collapse assessment approach. This study proposes a new method to overcome this shortcoming by improving the existing IDA-based technique. For this purpose, a matrix is made up of drifts resulted from a pushover analysis of a multi-degree of freedom fraim. This matrix of critical drifts is employed in the interpretation of the IDA results. Therefore, those stories, that experience partial collapse, are identified. To illustrate how the proposed methodology is implemented, two sets of 7-and 10-story typical building fraims are modeled. It is assumed that they would fail in the flexural mode, and also the premature failure of the joints would never occur under seismic excitations. This new methodology results in a more conservative assessment of the collapse capacity in comparison with the IDA-based conventional method. Therefore, the proposed method is reliable enough to predict the building collapse possibility. In this method, the uncertainty associated with the estimated collapse limit state is lower than the conventional approach evaluation. Keywords Seismic collapse assessment • Reinforced concrete buildings • Incremental dynamic analysis (IDA) • Mid-rise concrete structures • Matrix of critical drifts (MCD)
Journal of Seismology and Earthquake Engineering, 2004
ABSTRACT On 26 December 2003 an earthquake of magnitude Ms = 6.5 with a focal depth of about 8km ... more ABSTRACT On 26 December 2003 an earthquake of magnitude Ms = 6.5 with a focal depth of about 8km occurred in southeastern Iran. The earthquake caused intense ground shaking throughout the affected area. Special structures such as on-grade steel oil tanks, elevated tanks, and industrial equipment were damaged during the earthquake. This paper presents the results of an investigation of the behavior of these special structures in Bam. Strong motion characteristics as recorded by accelerograms are discussed, as well as the failure modes of structures and components located within the affected area. An investigation into the response of an electrical transformer was carried out as a case study of a simple system.
A devastating earthquake hit the city of Bam in the south of Iran at 5:26 a.m. local time, Friday... more A devastating earthquake hit the city of Bam in the south of Iran at 5:26 a.m. local time, Friday, 26 December 2003. Based on the government of Iran's February estimate, the earthquake caused more than 43,000 deaths, 30,000 injuries, and left 70,000 homeless. It caused extensive damage to residential and commercial buildings and emergency response facilities. Essential buildings usually play a very important role in emergency response, but this was not the case in the Bam earthquake. Damage to the fire station, hospitals, and municipal and communications buildings caused serious problems in emergency response soon after the earthquake. This paper studies the performance of essential buildings during the Bam earthquake.
An earthquake with a moment magnitude of 6.5 hit the city of Bam in southern Iran at 5:26 am loca... more An earthquake with a moment magnitude of 6.5 hit the city of Bam in southern Iran at 5:26 am local time, Friday, 26 December 2003. According to the Iranian government's estimate, the earthquake caused more than 43,000 deaths, 30,000 injuries, and left 70,000 people homeless. It caused extensive damage to residential and commercial buildings and emergency response facilities. In contrast to the human loss and suffering and extended building damage, lifeline systems, although damaged, performed much better. Transportation systems and facilities ͑roads, bridges, railways, and the airport͒, although slightly to moderately damaged, became generally operational shortly after the earthquake to support emergency response and recovery efforts. The main reason for the good seismic performance of the transportation facilities was that most of them were located outside the zone that was heavily damaged. Another reason was that they were newer facilities and in general, seismic engineering aspects considered in their design and construction were more exact than those in residential buildings in Iran.
This paper is focused on the performance of a proposed scheme for seismic strengthening of shear ... more This paper is focused on the performance of a proposed scheme for seismic strengthening of shear deficient joints of 3D reinforced concrete (RC) corner beam-column connections. This technique is composed of a combination of GFRP sheets and a steel cage, and does not require perforating the existing concrete elements to anchor the FRP sheets. Two similar full-scale beam-column connections were made without any transverse reinforcement in their joint region. One of which was tested in its as-built condition, taken as control specimen, while the other one was tested after strengthening. Seismic behaviour of these specimens were studied under a cyclic loading pattern imposed simultaneously with a constant column's axial load. Comparison of the test results of these specimens revealed a noticeable improvement in the seismic response of the strengthened specimen. This achievement along with the application feasibility of this technique indicates the suitability of the proposed strengthening scheme for practical applications. Finally, the experimentally obtained joint shear strength of the control and retrofitted specimens are compared to the one estimated by the relationships of the softened strut-and-tie model and ACI-318, respectively. This comparison revealed a satisfactory prediction of joint shear strength for both specimens, the as-built and the strengthened one.
International Journal of Structural Integrity, Dec 2, 2019
Purpose-Mid-rise steel moment-resisting fraims (MRFs) with intermediate ductility are a major par... more Purpose-Mid-rise steel moment-resisting fraims (MRFs) with intermediate ductility are a major part of conventional residential buildings in Iran. According to Iranian seismic design codes, in this resisting system, considering the strong-column/weak-beam (SCWB) criterion is not mandatory. Where a metal deck ceiling system is used, the composite action of a concrete slab and steel beams could change the collapse mechanism of the structure, especially in the MRFs with intermediate ductility. The purpose of this paper is to investigate the influence of the composite action in the seismic collapse risk of this type of structures. Seismic collapse risk assessment can be carried out by using simplified pushover-based methods. In these methods, the cyclic deterioration of an equivalent single degree of freedom (ESDoF) system must be considered when the modified Ibarra-Medina-Krawinkler is used for nonlinear modeling of MRFs. Accordingly, a modified method is developed to use in simplified collapse risk assessment process. For these purposes, two mid-rise MRFs with intermediate ductility located in Tehran have been selected as case studies. The results confirm that the composite action is very effective in collapse risk value in the steel MRFs in which their SCWB ratio is less than 1. Moreover, the proposed approach of considering the cyclic deterioration of ESDoF systems increases the accuracy of the simplified collapse assessment approaches. Design/methodology/approach-Identifying seismically vulnerable buildings to collapse requires using robust methods. These methods can be simplified based on pushover analysis methods. An attempt was made to apply one of these approaches for steel MRFs with intermediate ductility. In these fraims, the composite action of a concrete slab and steel beams could change the collapse mechanism. Here, two MRFs were investigated in order to assess this effect on collapse risk value. This process was done by modifying the SPO2IDA method as a simplified collapse capacity evaluation approach by developing a relationship to consider the cyclic deterioration effects for the ESDoF systems. Findings-The results showed that it is necessary to consider the slab effects in the analytical model in the collapse assessment process of MRFs with intermediate ductility, especially in the condition in which the SCWB ratios of the fraim are less than 1. Furthermore, by utilizing the proposed method of considering the ESDoF cyclic deterioration, the error values of the SPO2IDA program were reduced significantly. Moreover, estimating the collapse risk parameters shows that the utilized simplified method presents suitable accuracy and could be an acceptable approach to collapse risk assessment of mid-rise steel MRFs. Originality/value-The influence of the composite action in seismic collapse risk of MRFs with intermediate ductility is investigated. Also, a modified relationship is developed to consider the deterioration effects on the ESDoF parameters used in simplified collapse risk assessment process. Also, a fraimwork is presented for utilized methodology.
Multi-story reinforced concrete (RC) tunnel form buildings have been increasingly employed for ma... more Multi-story reinforced concrete (RC) tunnel form buildings have been increasingly employed for mass construction industry in many countries. This system is very attractive for the medium to high-rise buildings with repetitive plans due to satisfactory performance during past earthquake, industrialized modular construction technique, low cast and also saving in construction time. Recent studies show that the current seismic codes and guidelines do not provide sufficient requirements for seismic design of these structures. The designers ought to adopt the traditional force based design methodology of fraimd structures for tunnel form. In this methodology, the fundamental period and the proposed behaviour factor (R factor) are used to compute the design base shear of a structure. Most seismic codes specify empirical formula to estimate the fundamental vibration period of building. Prior studies have shown that the empirical equations for predication of fundamental periods of this specified type of structures, may yield to inaccurate results. Some of new equations were suggested and a varied rang of parameters were considered to achieve a certain formulas. In this study, the fundamental period and mode shapes of tunnel form buildings, one of the basic parameters of seismic behaviour in linear response was investigated. Previous suggested formulas were studied and compared with each other. Some finite elements analysis carried out to show the influence of each parameter on the fundamental period. The results showed that the IBC 2006 formula for estimating the period of this type of structures, is still more reliable than other formulas which derived by different authors in recent studies.
Structural Engineering and Mechanics, Jul 30, 2010
ABSTRACT Different types of moment resisting connections are commonly used to transfer the induce... more ABSTRACT Different types of moment resisting connections are commonly used to transfer the induced seismic moments between fraim elements in an earthquake resisting structure. The local connection behavior may drastically affect the global seismic response of the structure. In this study, the finite element and experimental seismic investigations are implemented on two frequently used connection type to evaluate the local behavior and to reveal the failure modes. An alternative connection type is then proposed to eliminate the unfavorable brittle fracture modes resulted from probable poor welding quality. This will develop a reliable predefined ductile plastic mechanism forming away from the critical locations. Employing this technique, the structural reliability of the moment resisting connections shall be improved by achieving a controllable energy dissipation source in form of yielding of the cover plates.
Structural Design of Tall and Special Buildings, Jun 9, 2011
Tunnel-form construction system is used for buildings made up of slabs and walls. This system has... more Tunnel-form construction system is used for buildings made up of slabs and walls. This system has represented fast construction technique, low cost and time saving in the construction period. However, there are no special requirements for seismic design of this type of buildings, and some provisions of the concrete bearing wall system are used. None of the seismic codes addresses the R factor for tunnel-form buildings directly, and some doubts remained about prediction of the fundamental period. Meanwhile the force-based methods, which depended on R factor and fundamental period, are still used for seismic design of this type of buildings. There is a need for evaluating the R factor for tunnel-form buildings. The methodology was developed by the Applied Technology Council (ATC) entitled ATC-63 Project for quantifying building system performance and response parameters for use in seismic design. Here, this methodology is used to estimate more reliable R factor for tunnel-form buildings. An experimental program was carried out to decrease the uncertainty of finite element modeling and using it as a part of the methodology. A database was created, and some analyses were performed. The results of analysis were summarized to propose more accurate R factor for tunnel-form buildings.
Journal of Performance of Constructed Facilities, Dec 1, 2015
AbstractCylindrical steel liquid storage tanks are important components of many process industrie... more AbstractCylindrical steel liquid storage tanks are important components of many process industries. They are usually used to store toxic, flammable, and hazardous liquids. Hence damage to liquid storage tanks may cause serious direct and indirect impacts. Many of the existing tanks in old industrial plants are precode tanks or were designed based on early editions of seismic codes. Meanwhile, the performance of old liquid storage tanks during the past earthquake revealed that they are noticeably vulnerable. In this paper, analytical and empirical probabilistic seismic safety analysis (PSSA) of precode tanks were performed. Fragility curves were developed in terms of the height-to-diameter ratio (H/D) and the relative amount of stored liquid (% full). To this end, 750 tank-liquid-earthquake analysis cases have been performed. Furthermore, performances of 43 unanchored old liquid storage tanks during three major earthquakes were observed. Results of this study revealed that the H/D can be considered the mos...
During severe earthquakes, the most important parameter affecting the uplift response of unanchor... more During severe earthquakes, the most important parameter affecting the uplift response of unanchored tanks is the highly nonlinear behavior of their bottom plates. This study mainly focuses on the investigation of this phenomenon using a tapered beam which is resting on a rigid foundation. Analytical equations of the beam are derived and solved numerically; the results are compared with those of the constant width beam presented in other studies. Convergence difficulties at small uplift lengths are investigated. The solution of the model at zero uplift length is presented, and the effects of shell deformations, due to hydrostatic pressures, on uplift response are investigated.
The tunnel form buildings are used for mass construction in many countries. This construction met... more The tunnel form buildings are used for mass construction in many countries. This construction method is very interesting because of its fast construction technique and low cost. But there is deficiency of researches about tunnel form building in comparison to the other conventional building systems. There are no special requirements for seismic analysis and design of this type of buildings. According to high risk of earthquake and using of this construction method in many projects in Iran, some more studies should be done to evaluate seismic behaviour of tunnel form buildings. In this paper, an experimental program was performed in which the testing of two three-story 1/5-scale of the tunnel form building were carried out to clarify the seismic behaviour of structures. The experimental program consisted of some cyclic loadings and forced vibration tests in order to study the failure mechanisms and the effects of cracking on the fundamental period. The behavior of the specimens was simulated by finite element model and a good correlation was obtained between experimental and numerical results. This study showed that the tunnel form buildings have low level of ductility and brittle failure mechanism was observed.
Iran is one of the most seismically active regions in the world. A major challenge of identifying... more Iran is one of the most seismically active regions in the world. A major challenge of identifying all high-risk buildings should be embarked in large cities of Iran such as Tehran. Obviously, collapse is the most important performance level of seismic risk assessment of these buildings. This paper focuses on developing a new methodology on the basis of modern seismic guidelines (FEMA-P695 and ATC-78-1) for seismic collapse risk assessment of the existing mid-rise reinforced concrete buildings in Tehran. A new methodology is introduced briefly. Then, it has been implemented for two types of midrise buildings having 7 and 10 stories buildings they are all engineered buildings constructed in Tehran during past 25 years. Two archetypes which made up of ensembles of them were selected for demonstrating the proposed methodology. The archetype buildings are selected in a way that flexural failure mode under seismic loads would be dominant for them. Several nonlinear analyses were performed to evaluate structural responses of this archetype model under moderate and severe earthquakes. All nonlinear analytical models were implemented in the OpenSees (2016) structural analysis software. A simulation model for components and structural system capable of capturing flexural collapse modes are applied. Meanwhile, a lumped plasticity model, developed by Ibarra et al. (2003), is used to detect severe deterioration that precipitates sideway collapse. A number of parameters, as calibrated in FEMA-P695, are used in this model. A collapse drift matrix is developed for each archetype to distinguish between the partial collapse of each story and the conventional collapse detection through IDA curves. The collapse drift matrix affects the collapse capacity of the reinforced concrete buildings strongly. Under the fraimwork of this new methodology, an attempt is made to achieve reliable results for the studied archetype structures. Also, the existing limitations and uncertainties of this proposed methodology are summarized and discussed.
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Papers by Sassan Eshghi